Stand straight against a flat wall with your heels, back, and head touching it
Remove shoes and any headwear
Keep your feet flat on the floor and legs straight
Look straight ahead with your chin level
Place a flat object, such as a book, on top of your head and mark the wall where it touches
Measure from the floor to the mark using a tape measure or ruler
Take the measurement in inches or centimeters
Repeat the measurement for accuracy
Measure at the same time of day each time if you want consistency